16 D. P. PENHALLOW— PAEKA DECIPIENS. 



But, as shown by the specimens, there are undoubtedly three forms to be distin- 

 guished. As some means of separating them seems desirable, I would suggest that they 

 be referred to one species and two varieties, the latter being converted into species, if 

 found desirable, on the basis of fiiture examinations of such new material as may be 

 available. The larger forms with the rugose stems and large oval fruit would properly 

 constitute the type Parka decipieiis, Flem. The fruits of the second dimension are the 

 representatives of the first varietal form a media, and the smaller fruits and stems, 

 together with the narrow linear leaves, would be /3 minor. 



The systematic description of these plants as thus developed might be stated as 

 follows : 



GrENUs Parka. Flem. 



Aquatic plants with creeping stems, linear leaves, and sessile sporocarps bearing two 

 kinds of sporangia. Sporangia, 2 mm. in diameter ; macrospores, 40 /' ; microspores, 15 A'. 



These fossils occur in micaceous, slaty or sandy shales. Their most characteristic 

 appearance is that of oval bodies or fragmentary masses showing rounded discs or impres- 

 sions of such. They are sometimes carbonized, often ferruginous. From the Lower 

 Devonian of Myreton, Rescobie, Blairgowrie, Thurso and Caithness, Scotland. (Reid and 

 Graham ) 



Parka decipiens, Flem. — Stems rugose, about 4 cm. in diameter, showing stumps of 

 branches about 11 cm. distant. Leaves linear, 1 cm. broad, with somewhat rounded 

 terminations. Sporocarps oval, 3"5 X 5'5 cm., bearing more or less conspicuous 

 impressions of the contained sporangia. 



The sporocarps are sometimes complete, though generally found in fragments, either 

 carbonized or ferruginous. 

 a media, n. var. Sporocarps oval, nearly entire, 13 X 20 mm. broad. Impressions of 

 sporangia distinct, usually carbonized. 

 This variety shows no conspicuous leaves or stems. 

 /? minor, n. var. Stems 4 mm. broad. Leaves linear, 15 to 2 mm. broad, sometimes 

 finely veined. Sporocarps oval, 6 to 11 mm. broad. Impressions of the sporan- 

 gia distinct, often carbonized. 



EXPLANATION OF PLATE I. 



Fig. 1.— Prothalli in various stages of growth, a The most complete form, flat and thalloid. / In an early stage 



of growth from the spore and spherical, x 300. 

 2a. — Microspores showing the cell-wall carbonized, x 300. 

 2b. — Maerospores showing the cell-wall carbonized, x 300. 

 3. — Sporocar2J showing the contained sporangia in an undeveloped state, x 4'2. 

 4. — Portion of a large sporocarp of Parka decipiens, showing the characteristic form and aggregation of the 



sporangia x 5"3. 

 5. — Sporocarp of variety a media, showing the outer membrane crushed olf at the top, and five sporangia in 



the depleted cavity, x 4'2. 

 6. — Discoid body resembling the fruit of Pdlolum. x 4. 

 7. — Parka decipiens, Flem., var. /i minor. Pen. Natural size. 



